The present invention relates to an image processing device capable of writing two lines at a time which is advantageously applicable to a copier, facsimile apparatus, printer or similar apparatus using digital image data.
Technologies relating to density conversion in the subscanning direction for single beam writing applications are disclosed in, e.g., Japanese Patent Laid-Open Publication No. 7-87321. This document pertains to an image data processing device of the type recognizing the shape of a line at a boundary between a black dot area and white dots which are arranged in a bit map, transforming the characteristic of the line recognized on a dot basis to bit code information, using a part of the code information to determine whether or not data needs correction, and executing correction with dots needing correction in accordance with the code information. The technology taught in the above document is characterized by image data generating means capable of repeatedly generating identical image data arranged in a bit map at the same timing for any desired signal waveform. For example, the image data generating means reads bit map data out of a memory twice in order to double the density of the data in the subscanning direction.
However, the above conventional technology does not effect density conversion in the main scanning direction and is limited to double density control in the subscanning direction.